Re: Why the "where NOT EXISTS" does not work?

TurkBear wrote:
>
> Try
> select a from A_Table
> minus
> select a from B_table
>
> This will give you all a from A_table NOT in B_table
>
> C Chang <cschang_at_maxinter.net> wrote:
>
> >I have 2 tables say A_table, B_table. They both have some common
> >columns. The A_Table has some rows that with the column not appearing
> >in B_table. I tried to use following to find out what appears in
> >A_talbe but not in B_table.
> > select a
> > from A_table
> > where NOT EXISTS
> > ( select a
> > from B_table
> > where ..);
> >and it always return 0 row. What went wrong? Need Help Thanks.
> >
> >C Chang
>
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Which Proccess is more efficient?

select a from A_Table
minus
select a from B_table

or

select a from test1
where not exists
(select 1 from test2
  where test1.a = test2.b)

C Chang Received on Wed Oct 24 2001 - 22:17:49 CDT